1. Field of the Invention
The invention relates to a low profile surface mount coaxial connector that permits both axial and radial float relative to a mating connector.
2. Description of the Related Art
A coaxial cable includes an inner conductor and an outer conductor that surrounds the inner conductor. Insulating or dielectric material typically is disposed between the inner and outer conductors to maintain the substantially concentric relationship therebetween. The inner conductor is used for carrying a signal, and the outer conductor functions as a shield. Thus, the signal carried by the inner conductor will not affect nearby electronic equipment, and conversely nearby electronic equipment will not adversely affect the signal carried by the inner conductor.
A coaxial connector may be mounted to an end of a coaxial cable so that the conductors of the cable can be connected to another coaxial cable, to an apparatus or to a circuit board. The coaxial connector includes a center contact that is connected to the inner conductor of the cable and an outer contact that is connected to the outer conductor of the cable. An insulation or dielectric material may be disposed between the inner and outer contacts to maintain a substantially coaxial relationship. Coaxial connectors typically are provided as a male and female pair of connectors configured so that the inner and outer contacts of one connector in the pair telescope into electrical contact with the inner and outer contacts of the mating connector.
Connections often must be made between one or more coaxial connectors on one panel or circuit board and a corresponding number of coaxial connectors on another panel or circuit board. These connections typically are made by placing the panels or circuit boards in opposed relationship to one another so that the connectors on one panel or circuit board face the connectors on the opposed panel or circuit board. The panels and circuit boards then are moved toward one another so that the respective connectors mate. The ability to mate the opposed pairs of panel-mounted or board-mounted electrical connectors in this manner depends partly upon the precision of mounting the connectors on the panels or boards. Even small mounting errors can significantly complicate the connection and can significantly increase the forces required to achieve proper mating. Excessive force on either panel or board can damage the panel or board and the circuits thereon. Accordingly, some coaxial connectors are configured to float transversely and/or radially relative to the panel or circuit board to facilitate alignment for mating. Coaxial connectors that are configured to float relative to the panel or circuit board are shown in U.S. Pat. Nos. 4,358,174 and 5,769,652.
There have been substantial efforts in recent years to reduce the size of electrical and electronic components. The electronics industry also is very competitive and continually seeks ways to reduce costs. The above-described U.S. Pat. No. 4,358,174 and much of the other prior art achieves a panel-to-panel connection by providing separate mateable connectors on each panel and then urging the mateable connectors into connection with one another. Significant size and cost savings have been achieved in some electrical connection art areas by employing surface mounting (e.g., surface mounted IC chips). A surface mount connector enables a connector on one panel to be connected directly to conductive regions on a mating panel. The known surface mount technology is not well suited for coaxial connectors in view of the need to provide shielding across the connection. A few attempts have been made to mount a small coaxial receptacle to conductive regions on a board and then to mate a coaxial plug with the receptacle. Such a connection is shown in U.S. Pat. No. 5,662,480. The above-described alignment problems that exist for panel-to-panel connections of coaxial connectors also exist for surface mounted connections.
In view of the above, it is an object of the subject invention to provide a coaxial connector assembly that enables axial and/or radial float for achieving panel-to-panel coaxial connections.
It is also an object of the subject invention to provide a low profile coaxial connector that is well suited for panel-to-panel connections.
The subject invention relates to a coaxial connector for achieving connection between signal carrying circuits on first and second opposed circuit boards and for achieving a grounding connection and shielding between the first and second circuit boards. The first circuit board is provided with a plurality of conductive regions printed or otherwise disposed thereon. The conductive regions on the first circuit board include a first signal carrying region and a first ground that may substantially concentrically surround at least a portion of the signal carrying region. Similarly, the second circuit board may be provided with a plurality of conductive regions printed or otherwise disposed thereon. The conductive regions on the second circuit board may include a second signal carrying region and a second ground that may at least partly surround the signal carrying region. The signal carrying regions and the ground regions on the respective circuit boards are connected to other signal carrying circuit elements and ground circuit elements by techniques that are known to those skilled in this art.
The coaxial connector may be used with a short cylindrical electrically conductive guide sleeve that has a mounting end, a mating end and an inner circumferential surface extending between the ends. The mounting end of the guide sleeve is secured to the first circuit board and is connected electrically to the first ground region on the first circuit board. Additionally, the guide sleeve is mounted substantially concentrically around the first signal carrying region on the first circuit board. The inner circumferential surface of the guide sleeve may be substantially cylindrical at locations adjacent the mounting end of the guide sleeve. However, the inner circumferential surface of the guide sleeve may be chamfered to define an outward taper adjacent the mating end.
The coaxial connector includes an outer contact assembly with a generally tubular base. The base has a mounting end, a mating end and an inner circumferential surface extending between the ends. The mounting end of the base is fixed to the second circuit board and is connected electrically to the second ground. The mating end of the base may be characterized by an inwardly extending flange with an inside diameter less than the inside diameter of the inner circumferential surface of the base at locations spaced from the flange.
The outer contact assembly further includes a floating outer contact with a mounting end, a mating end and inner and outer circumferential surfaces extending between the ends. The floating outer contact preferably includes an outwardly extending flange at the mounting end. The outwardly extending flange of the floating outer contact is disposed between the second circuit board and the flange at the mating end of the base of the outer contact assembly. The flange at the mounting end of the floating outer contact defines an outside diameter that is greater than the inside diameter of the flange at the mating end of the base of the outer contact assembly. However, the outer diameter of the flange at the mounting end of the floating outer contact is less than the inside diameter of the inner circumferential surface of the base at locations adjacent the flange. The outside diameter of the floating outer contact at locations adjacent the flange are less than the inside diameter of the flange at the mating end of the base. Thus, the floating outer contact can float both radially and axially relative to the base of the outer contact assembly, but cannot be separated from the base of the outer contact assembly.
The mating end of the floating outer contact may have an inwardly extending flange. However, portions of the inner circumferential surface of the floating outer contact between the inwardly extending flange and the mating end preferably are substantially continuously cylindrical. The outer circumferential surface of the floating outer contact preferably is chamfered adjacent the mating end to facilitate alignment and to generate float during mating.
Portions of the floating outer contact between the mating end and the base of the outer contact assembly may include an outwardly extending bearing flange. The bearing flange defines an outside diameter that exceeds the inside diameter of the inwardly extending flange on the base of the outer contact assembly.
The outer contact assembly further may include also a spring between the inwardly extending flange of the base and the outwardly extending flange at the mounting end of the floating outer contact. The spring may be configured to urge the floating outer contact towards the second circuit board. The outer contact assembly may further include a spring between the bearing flange of the floating outer contact and the inwardly extending flange of the base of the outer contact assembly. The spring washer biases the floating outer contact away from the second circuit board.
The coaxial connector further includes an inner contact assembly that is disposed substantially concentrically within the outer contact assembly and that extends from the second circuit board substantially to the mating end of the floating outer contact. The inner contact assembly includes a plunger and a receptacle that are capable of axially floating relative to one another while achieving a sliding electrical contact therebetween. In a preferred embodiment, the plunger extends from the second circuit board, and the receptacle extends from the plunger to the mating end of the floating outer contact. At least one of the plunger and the receptacle may be configured to achieve radial float therein. Additionally, the inner contact assembly may be configured to achieve radial float relative to the second signal carrying circuit element on the second circuit board.
The coaxial connector further includes a plurality of non-conductive elements between the inner and outer contact assemblies. The non-conductive elements function to substantially center at least portions of the inner contact assembly relative to at least portions of the outer contact assembly. The non-conductive elements between the inner and outer contact assemblies preferably include at least one resilient O-ring, and preferably a stacked array of resilient O-rings. The number of O-rings and the combined axial dimensions of the O-rings are selected to bias the plunger and receptacle of the inner contact assembly into an extended position and toward the first circuit board. However, the O-rings can be compressed resiliently in response to forces generated during mating.
The coaxial connector is employed merely by positioning the first and second circuit boards in substantially juxtaposed relationship to one another and then urging the first and second circuit boards toward one another. The chamfer on the outer surface at the mating end of the floating outer contact will engage the chamfered entry to the guide sleeve on the first circuit board. The engagement of these chamfers will help to guide the first and second circuit boards into proper alignment with one another and will generate radial float of the floating outer contact to permit the floating outer contact to telescope into the guide sleeve. The outside diameter of the floating outer contact is significantly less than the inside diameter of the guide sleeve. Hence, there are minimal connecting forces created during mating. Movement of the first and second circuit boards toward one another will urge the mating end of the floating outer contact into engagement with the first ground circuit printed or otherwise disposed on the first circuit board. Substantially simultaneously, the mating end of the inner contact assembly will contact the first signal carrying circuit element on the first circuit board.
The receptacle and plunger of the inner contact assembly may telescope relative to one another in response to axial forces generated as the first and second circuit boards are moved into their final position. In all such positions, the resilient O-rings will exert biasing forces that urge the mating end of the inner contact assembly against the signal carrying circuit element on the first circuit board. The resilient force exerted by the inner contact assembly can be varied by providing more or fewer resilient O-rings, and replacing any such O-rings that are removed by non-resilient spacers. Thus, greater axial float can be achieved with a larger number of resilient O-rings.
Plural coaxial connector assemblies are likely to be used simultaneously at different locations on the first and second circuit boards. The radial and axial float of the floating contact members may vary from one coaxial connector assembly to another.